A retired Austrian army colonel has been charged with spying for Russia for at least a quarter of a century and faces up to 10 years in prison if convicted.

Prosecutors in Salzburg said on November 8 that the 71-year-old man, identified as Martin M., had allegedly worked for Russia's GRU military intelligence since 1993, providing it with detailed information about Austrian weapons systems and military data.

'Investigations revealed the defendant's integration into a structured, state-run agent network,' the prosecutor's office said in a statement.

According to the statement, the officer received hundreds of thousands of euros in exchange for his services, which he continued even after retiring.

The man was detained last year after Austrian authorities caught him while receiving money from his alleged handling officer.

Russian Foreign Minister Sergei Lavrov said at the time that he knew 'nothing about the issue.'

Austria is one of the few European countries that has maintained close diplomatic contacts with Moscow -- despite Russia's actions in Ukraine, and even after the poisoning of ex-Russian spy Sergei Skripal and his daughter in Britain which London has blamed on the Kremlin.

Vienna, home to multiple international organizations such as the International Atomic Energy Agency (IAEA), the Organization for Security and Cooperation in Europe (OSCE), and a branch of the United Nations, is known as a European espionage hub.

The city also used to be a gateway to communist countries during the Cold War because of its proximity to Eastern Europe.